Section 3

• Fertilization occurs in a fallopian tube. Pregnancy begins when a blastocyst implants itself in the lining of the uterus.

• The three primary germ layers—the ectoderm, mesoderm, and endoderm—form early in embryonic development. Four membranes—the amnion, yolk sac, allantois, and chorion—also form early in embryonic development.

• Nutrients, gases, and other substances pass through the placenta by diffusion from the mother to the fetus.

Discover How To Sleep In Peace And Harmony In A World Full Of Uncertainty And Dramatically Improve Your Quality Of Life Today! Finally You Can Fully Equip Yourself With These “Must Have” Tools For Achieving Peace And Calmness And Live A Life Of Comfort That You Deserve!